Silica-based glass, such as soda-lime-silica glass, is prevalent in the manufacture of glass containers and other articles. Molten glass used to make such articles is conventionally prepared by melting a mixture of glass-forming materials known as a batch in one end of a continuous tank furnace. The resulting molten glass typically contains an undesirable amount of gas bubbles, commonly referred to as seeds. The gas bubble content of this unrefined molten glass is typically reduced to a desirable level by heating the molten glass to a relatively high temperature to reduce the viscosity of the molten glass so that gas bubbles within the molten glass can gradually rise to a free surface thereof and escape in a suitable amount of time. In such processes, rising convection currents within the molten glass are typically relied upon to bring the gas bubbles to the surface of the molten glass.
A general object of the present disclosure, in accordance with one aspect of the disclosure, is to provide an apparatus and a process for increasing the rate at which gas bubbles are released and/or removed from a flow of molten glass, as compared to conventional refining processes. The apparatus and process of the present disclosure also may reduce the temperature at which the molten glass must be heated to effectively refine the molten glass.
The present disclosure embodies a number of aspects that can be implemented separately from or in combination with each other.
A porous body for refining a stream of molten in accordance with one aspect of the disclosure includes: an inlet, an outlet in fluid communication with the inlet and spaced apart from the inlet in a longitudinal direction, and a plurality of pores through which molten glass can flow between the inlet and the outlet. The pores of the porous body are defined by walls having wall surfaces that are configured to interact with the molten glass as the molten glass flows between the inlet and the outlet to help refine the molten glass. This may be accomplished by promoting release of gas bubbles from the molten glass, for example, by promoting coalescence of the gas bubbles within the molten glass or by increasing the size of the gas bubbles within the molten glass. In other embodiments, this may be accomplished by reducing the size of the gas bubbles within the molten glass to a commercially acceptable size.
In accordance with another aspect of the disclosure, there is provided an apparatus for melting and refining molten glass that includes: a melter, a refiner downstream of the melter, a throat between the melter and the refiner, and a porous body having an inlet and an outlet in fluid communication with the inlet. The porous body may be disposed within the melter, the refiner, and/or the throat. The porous body includes a plurality of pores through which molten glass can flow between the inlet and the outlet. The pores of the porous body are defined by walls having wall surfaces that are configured to help refine the molten glass. For example, the wall surfaces may be configured to promote coalescence of gas bubbles within the molten glass to increase the size of the gas bubbles, or the wall surfaces may be configured to reduce the size of gas bubbles within the molten glass to a commercially acceptable size. In some embodiments, the wall surfaces may be configured to interact with the molten glass to produce carbon dioxide (CO2) gas, nitrogen oxide (NOx) gas, or both.
In accordance with yet another aspect of the disclosure, there is provided an apparatus for melting and refining molten glass that includes: a meter having an upstream end and an opposite downstream end; a throat in fluid communication with the downstream end of the melter; and a porous body having an inlet, an outlet in fluid communication with the inlet, and a plurality of pores through which molten glass can flow between the inlet and the outlet. The porous body is configured to intercept molten glass that is flowing from the downstream end of the melter into the throat and to interact with the molten glass to promote release of gas bubbles from the molten glass or to reduce the size of the gas bubbles within the molten glass to a commercially acceptable size.
In accordance with another aspect of the disclosure, there is provided a process for refining molten glass in which molten glass is provided that includes a plurality of gas bubbles. A porous body is also provided that includes an inlet, an outlet in fluid communication with the inlet, and a plurality of pores through which molten glass can flow between the inlet and the outlet. The plurality of pores of the porous body are defined by walls having wall surfaces. The molten glass is flowed through the porous body and through the plurality of pores such that interaction between the molten glass and the wall surfaces of the pores promotes release of gas bubbles from the molten glass, or causes at least some of the gas bubbles within the molten glass to collapse or rupture to reduce the size of the gas bubbles to a commercially acceptable size.